Hideki Motosuwa (本須和秀樹 , Motosuwa Hideki?) is a 19-year-old (18 in the anime) repeat student (ronin) attempting to get into university by studying at Seki cram school, which his parents have sent him to. They have also severed his allowance, which means he has to work at Yorokonde (My Pleasure), an izakaya, to make ends meet. One night, while walking home from work, he finds a persocom lying in a pile of garbage. He takes her home, and after much searching, switches her on and finds that the only word she can utter is "Chi". Because of this, he gives her the name "Chi" and takes her into his care, doing his best to protect and teach her.
Hideki could best be described as "a fish out of water." Living in the country his entire life, Hideki has trouble adjusting to his new life in Tokyo. Due to this, he is prone to outbursts of confusion and frustration. Also, because of the time spent by himself on his family's farm (which in the anime is revealed to be in Hokkaidō), Hideki has a habit of thinking out loud and talking to himself. This leads to some very entertaining moments between himself and the women he meets. Like many young men, Hideki has an active libido, possessing many pornographic magazines which he refers to as "okazu" ("side dish"). (In the English manga translation, Chi refers to one of the magazines as a "tasty side dish"; in the anime's American translation, Chi refers to these magazines as "Hideki's yummies"). When he moves to Tokyo, Hideki desires a persocom so that he can finally surf the internet for pornography. It should be stated however that he isn't the only character who thinks this way. In fact Shinbo himself proudly admits that Plum is also equipped to perform these tasks when he first meets Hideki.
Despite his shortcomings and occasional moments of awkwardness with the bustling environment of Tokyo, Hideki is a genuinely kind and honest person, whose habit of thinking of others' well-being before his own can cause many problems. When a friend is in trouble, especially Chi, he is always there to help. Although many characters in the series often tease him for being a "nice guy", they turn to him for advice with their problems, knowing he will always hear them out and do his best to assist them.